The impossibility of separating age, period and cohort effects

Soc Sci Med. 2013 Sep;93:163-5. doi: 10.1016/j.socscimed.2013.04.029. Epub 2013 May 4.


This commentary discusses the age-period-cohort identification problem. It shows that, despite a plethora of proposed solutions in the literature, no model is able to solve the identification problem because the identification problem is inherent to the real-world processes being modelled. As such, we cast doubt on the conclusions of a number of papers, including one presented here (Page, Milner, Morrell, & Taylor, 2013). We conclude with some recommendations for those wanting to model age, period and cohort in a compelling way.

Keywords: Age–period–cohort models; Collinearity; Model identification.

Publication types

  • Comment

MeSH terms

  • Employment / statistics & numerical data*
  • Female
  • Humans
  • Male
  • Suicide / statistics & numerical data*